Biosynthesis, metabolism and biological role will be studied of furan fatty acids which have been discovered in liver and testes lipids of certain freshwater fish. Methods for chemical and radiochemical synthesis of the natural and closely related furan fatty acids will be perfected. Using likely precursors, their biosynthesis will be studied and the synthesizing tissues identified. Further work will characterize the subcellular fractions and enzymic processes involved. We expect to use trout, northern pike, carp, blue gill and other fish indigenous to the Midwest, which have the furan fatty acids at high levels in male liver and in testes during or before spawning time. Dietary, in vivo and in vitro experiments will be carried out to elucidate their biosynthesis and conversions.